Electroanatomic and Pathologic Right Ventricular Outflow Tract Abnormalities in Patients With Brugada Syndrome

Background: The prevalence and significance of structural abnormalities in Brugada syndrome (BrS) are still largely debated. Objectives: The authors investigated the relationship between genetic background, electroanatomic abnormalities, and pathologic substrate in BrS. Methods: They performed 3-dimensional electroanatomic unipolar and bipolar mapping in 30 patients with BrS. Twenty patients underwent 3-dimensional electroanatomic unipolar and bipolar mapping–guided right ventricular outflow tract (RVOT) endomyocardial biopsy. Programmed ventricular stimulation and genetic analysis were performed in all patients. Results: Low-voltage areas (LVAs) were observed at unipolar map in 93% of patients and at bipolar map in 50% of cases. Unipolar LVAs were always larger than bipolar LVAs, were always colocalized, and in all cases included RVOT. Disease-causing mutations were detected in 10 (33%) patients. Programmed ventricular stimulation was positive in 16 cases (53%). In 75% of patients, RVOT histology showed pathologic findings with myocardial inflammation in 80% of them. Among patients with abnormal bipolar map submitted to endomyocardial biopsy, 9 (81%) showed evidence of myocardial inflammation. Conversely, bipolar map was abnormal in 83% of patients with myocardial inflammation. Myocardial inflammation was also more prevalent among inducible patients (83% vs. 25% in noninducible; p = 0.032). Conclusions: BrS is characterized by electroanatomical and structural abnormalities localized to RVOT with a gradient of the pathologic substrate from epicardium to endocardium possibly driven by myocardial inflammation. These findings reclassify BrS as a combination of structural and electrical defects opening the way to new risk stratification and therapeutic strategies.